This invention concerns improvements relating to the etching of thin films.
Along with the development of ULSI devices, high precision patterning technologies have been of great importance. There are two types of etching process for producing patterns. Dry etching is the method which is carried out with a gasesous etchant based largely on its phisical attack to surfaces to be etched rather than corrosive attack. Wet etching is representatively based on chemical corrosion of surfaces to be etched, for example, by means of acid. Since the former tends to give rise to damage of the surface due to the bombardment of excited species, some kinds of thin films can not be treated by this method if the surface underlying the thin films is made of a material which is vulnerable to the attack of the bombardment. The wet etching in turn has a shortcoming in that, when the underlying film to be patterned is made of a material which is not easily attached by chemicals but vulnerable to the bombardment, it is too difficult to select a corrosive etchant which is sufficiently corrosive to etch the film and a material for use in forming masks which has to endure the attack of the strong etchant.